1. Field of Invention
The present invention relates to ball joints used in suspension systems of vehicles, and particularly to dust boots for ball joints designed for high angles of articulation.
2. Description of the Prior Art
Those skilled in the art will appreciate the typical issues related to longevity of original equipment ball joints employed in suspension and steering systems of vehicles. Many of such applications require the use of protective elastomeric boots, commonly called dust boots or protective caps that are installed over the connected ball joint assembly. Such boots or caps are particularly critical in environments subject to contaminants including dirt and debris. In applications involving high angles of articulation, such as in long or wide swing ball studs, the boots are prone to cracks and or fracture, which in turn leads to premature demise of the ball joint assembly. Usually a failure of a ball joint involves not only replacement of the ball joint; typical requirements call for the associated mating boss part to be replaced as well. Thus premature replacement of ball joint assemblies can be relatively expensive.
In marine (water submersible) applications, the noted issues become potentially exacerbated. For example, an amphibious vehicle is capable of operations both on land and in water. Thus, admission of dust into an exposed ball joint assembly over land, in combination with water entrainment while in water, can be particularly deleterious to a ball joint assembly, and can lead to premature failure, particularly where high ball joint angles of articulation are involved. Moreover, such premature deterioration of the ball joint assembly may be aggravated if the joint is subject to substantial twisting or rotational movements about the longitudinal axis of stud.
The present invention provides an improved dust boot adapted to accommodate a ball and socket joint for marine applications subject to high articulation under the relatively harsh conditions noted. The improved boot is capable of accommodating an arc of articulation of an associated ball stud up to at least 60 degrees of swivel center of the joint, as well as twisting or rotary motions of the stud of at least 45 degrees from a rotational center. The dust boot includes multiple undulations that feature a series of convolutions or deep folds for this purpose.
In one example, the boot contains at least one undulation that includes two pairs of radially extending ribs so as to provide a convoluted bulbous loop, complete with reverse bends so as to maximize amount of material available for stretching as the stud is articulated to high angles. In addition, the abundance of material provided by the bulbous loops not only provides for the noted stud articulation, but also accommodates the noted rotary motions without potential deleterious effects.
In the same example, the materials used to form the dust boot can include thin thermoplastic polyurethanes, or thermoplastic injection molded or thermoset elastomers. Ideally, the material is waterproof so as to accommodate ball joints used in suspension control arms of water submersible vehicles.